Clear doesn't let you skip security. It basically just allows you to cut to the front of the line for a fee. You still have to go through the x-ray machines, etc.
TSA Pre actually does reduce security requirements (e.g. you can keep your shoes on...) in exchange for, I've always assumed, a mini-background check when you apply for the program.
> mini-background check when you apply for the program.
You'll get fingerprinted, etc., and while it's nothing like a serious security clearance, they do look you up rather thoroughly.
Note: my only direct knowledge comes from applying to Global Entry, which is a pickier program, but Precheck does collect biometrics (at least facial and fingerprints). Global Entry was around 15 minutes for the interview process (both formal and informal; I knew the two guys outside the interview and fingerprint room didn't really just want to talk to me to pass the time), but that was a decade ago.
One interesting anecdote from my interview is that I was told that the #1 reason Global Entry applications failed at the time was that one of the questions was whether or not you had ever been arrested - not convicted - and people would say no. Not an auto-disqualifier to have been arrested, but lying about it was.
TSA Pre actually does reduce security requirements (e.g. you can keep your shoes on...) in exchange for, I've always assumed, a mini-background check when you apply for the program.